Custom dual master cylinder mount. Clearance concern

[40desoto]

I fabricated a mock mount for a dual master cylinder for my 1940 Desoto Coupe. All seems to align and well but noticed the pedal hits the to of the master cylinder when pressed all the way down.  Would this limit the full travel needed for the brakes to operate properly?  Should I concerned and rethink this bracket or wait until brakes are installed and test with fluid pressure in the system.

any other mount ideas others have used to mount a dual master cylinder into this Setup.

 

 

[Sniper]

Since you have no lines attached I assume this is a dry fit test.  So based on this, here are my thoughts.

 

In normal operation the piston in the M/C will never bottom out, so the pedal may not hit.

 

However, we knew this was coming, if you do spring a leak in one circuit or the other then the piston in the M/C will likely travel further causing them to hit and this could lessen your braking availability right when you need it most. 

 

Based on that thinking I would see how much further the push rod needed to travel to bottom out and maybe clearance a bit off the pedal arm where they hit.  If that isn't likely to do the trick then it looks like you will have to move the M/C further forward, assuming you have the room.

 

You could think about relocating the pushod location at the pedal end so that the piston in the M/C bottoms before the pedal hits but that will affect your pedal ratio.  this could potentiall make your pedal feel too hard or not give you enough mechanical leverage to have good brakes.  It's all a balance. 

 

Alternatively, Wilwood makes M/C with vertical mounting ears, rather than the horizontal ones you have.  The link will also give you dimensions to see if it might fix your interference. 

 

https://www.wilwood.com/MasterCylinders/MasterCylinderProd?itemno=260-7563

 

not sue of there is an OEM M/C with vertical mounting ears though.

[Bobb Horn]

On my 38 Coupe, I used a small piston 1986 Dodge MC for 10 years, and then I installed a large piston 1994 Ford Bronco MC.

The MCs were aluminum, so easy to cut some of the mounting off, and redrill new mounted holes.    The brakes pedals go all the way to the floor now...

 

[James_Douglas]

I tried to use a long custom push rod on my '49. I did not like the way it felt. Too much flex. I would also NEVER use those long nuts on a push rod. They are not designed for the load. If you are using that push rod as a template and make a single push rod then I think the length you are using would be fine. I would make sure that with each side failing that you could lock the remaining 2 brakes before the pedal hits the floor board.  I use remote fill on all my cars.

 

Also, keep in mind that MOPAR used two pedals and push rods. One for the regular brakes and one later on for the first power brakes. They have different ratios.

 

James.

[Sam Buchanan]

1 hour ago, James_Douglas said:

I tried to use a long custom push rod on my '49. I did not like the way it felt. Too much flex. I would also NEVER use those long nuts on a push rod. They are not designed for the load. If you are using that push rod as a template and make a single push rod then I think the length you are using would be fine. I would make sure that with each side failing that you could lock the remaining 2 brakes before the pedal hits the floor board.  I use remote fill on all my cars.

 

Also, keep in mind that MOPAR used two pedals and push rods. One for the regular brakes and one later on for the first power brakes. They have different ratios.

 

James.

 

Using threaded rod in such a critical application is also outside my comfort level. Here is the pushrod I fabricated when I mocked up a dual-chamber master cylinder:

 

 

It uses the ends of the stock pushrod which can be pressed back into use in the original configuration if needed. The pushrod is steel tubing with nuts welded on each end. The eye fitting screws into one of the nuts (with a jam nut), and the threaded shank of a grade 8 bolt threads into the other end (jam nut not shown in this photo). Very strong and stiff.

Edited February 15, 2020 by Sam Buchanan

[James_Douglas]

13 hours ago, Sam Buchanan said:

 

Using threaded rod in such a critical application is also outside my comfort level. Here is the pushrod I fabricated when I mocked up a dual-chamber master cylinder:

 

 

It uses the ends of the stock pushrod which can be pressed back into use in the original configuration if needed. The pushrod is steel tubing with nuts welded on each end. The eye fitting screws into one of the nuts (with a jam nut), and the threaded shank of a grade 8 bolt threads into the other end (jam nut not shown in this photo). Very strong and stiff.

I made the one for the 1949, I ended up not using it as it was 26 inches long and the dual cylinders had just more flex than I liked, was made from solid steel rod I got from Aircraft Spruce with a USA mill certificate. We machines the ends for heim joints. Could life up the car with it. I am not a fan of welding such things unless the welder is certified for that material and even then I would send it out for a x-ray to look for micro cracks. 

 

I have long been critical of welding on things that are in the brake system or the steering system that are not done "by the book" so to speak. Don't get me started on people who cut and weld spindles...

 

James.

[40desoto]

14 hours ago, Sam Buchanan said:

 

Using threaded rod in such a critical application is also outside my comfort level. Here is the pushrod I fabricated when I mocked up a dual-chamber master cylinder:

 

 

It uses the ends of the stock pushrod which can be pressed back into use in the original configuration if needed. The pushrod is steel tubing with nuts welded on each end. The eye fitting screws into one of the nuts (with a jam nut), and the threaded shank of a grade 8 bolt threads into the other end (jam nut not shown in this photo). Very strong and stiff.

Thank you Sam,  ill be doing that once I figure out the final lenght needed

[40desoto]

16 hours ago, Bobb Horn said:

On my 38 Coupe, I used a small piston 1986 Dodge MC for 10 years, and then I installed a large piston 1994 Ford Bronco MC.

The MCs were aluminum, so easy to cut some of the mounting off, and redrill new mounted holes.    The brakes pedals go all the way to the floor now...

 

Thank You Bob.  Are you running discs in the front and drums in the back? 

[Sam Buchanan]

5 hours ago, James_Douglas said:

I made the one for the 1949, I ended up not using it as it was 26 inches long and the dual cylinders had just more flex than I liked, was made from solid steel rod I got from Aircraft Spruce with a USA mill certificate. We machines the ends for heim joints. Could life up the car with it. I am not a fan of welding such things unless the welder is certified for that material and even then I would send it out for a x-ray to look for micro cracks. 

 

I have long been critical of welding on things that are in the brake system or the steering system that are not done "by the book" so to speak. Don't get me started on people who cut and weld spindles...

 

James.

 

Actually this one is 4130 0.049" tube left over from one of my aircraft builds, the welds are always under compression. I'm not officially certified but I have flown aircraft with a steel tube fuselage that I welded.     This pushrod is the same design as control surface pushrods that have been used on thousands of aircraft.

 

The dual-chamber mod I fabricated mechanically worked very nicely, no flex, I just couldn't get a good pedal with the particular cylinder I used.

 

Edited February 15, 2020 by Sam Buchanan

[Matt Wilson]

On 2/14/2020 at 12:17 PM, Sniper said:

Alternatively, Wilwood makes M/C with vertical mounting ears, rather than the horizontal ones you have.  The link will also give you dimensions to see if it might fix your interference. 

 

https://www.wilwood.com/MasterCylinders/MasterCylinderProd?itemno=260-7563

 

not sue of there is an OEM M/C with vertical mounting ears though.

I ended up selecting a similar Willwood master cylinder for my '49 Power Wagon.  I'm in the process of installing it now.  One thing I will point out is that my Willwood unit, and probably many other Willwood units, if not all of them, come with a disclaimer that says they are not DOT-approved for highway use, or similar wording.  I decided I wanted dual circuit brakes, and since an extensive search had not produced anything that would fit in that very tight space, I went ahead and purchased the Willwood unit. 

 

I've known of other people who have successfully used these units in vintage car applications for many years, and I think mine will work just fine and be every bit as reliable as any other master cylinder, but if I should get into a wreck, I could be under additional scrutiny by law enforcement, insurance and/or lawyers for having such a part on my truck.  I've heard of people's vintage or specialty cars being torn apart at the accident scene by investigators who were looking for modifications such as these, so don't he lulled into the mindset that they won't be discovered.  Eventually, I may try to find something else that is DOT-approved to fit the bill.  I just wanted everyone to be aware of this potential risk, and I'd also like to hear others' opinions and experiences in this regard.

Edited February 15, 2020 by Matt Wilson

[Bobb Horn]

12 hours ago, 40desoto said:

On ‎2‎/‎14‎/‎2020 at 5:49 PM, Bobb Horn said:

On my 38 Coupe, I used a small piston 1986 Dodge MC for 10 years, and then I installed a large piston 1994 Ford Bronco MC.

The MCs were aluminum, so easy to cut some of the mounting off, and redrill new mounted holes.    The brakes pedals go all the way to the floor now...

 

Thank You Bob.  Are you running discs in the front and drums in the back? 

I am running drums front, and rear...   Both MCs worked good...

 

[James_Douglas]

20 hours ago, Sam Buchanan said:

 

Actually this one is 4130 0.049" tube left over from one of my aircraft builds, the welds are always under compression. I'm not officially certified but I have flown aircraft with a steel tube fuselage that I welded.     This pushrod is the same design as control surface pushrods that have been used on thousands of aircraft.

 

The dual-chamber mod I fabricated mechanically worked very nicely, no flex, I just couldn't get a good pedal with the particular cylinder I used.

 

Funny you should say that...

 

I have been reading over Dud Davisson's articles in Sport Aviation on welding.  I have not done much welding since High School. I was taught both gas and stick at that time. We are going to the AAA in Iowa this fall to figure out what old aircraft we want to go looking for.

 

When I was in high school I built a Hot Rod '31 Model "A" coupe. One of the things I did was put a Mustang Steering box in it. I had been through a couple of bad professional welders at that point in time doing things I did not feel up to doing. After going through a few welders I tan across a guy that had been one of the army of people that got downsized by the close of the Apollo Program.

 

This man moved into Northern California and started a welding shop. He did welds on the Lunar Lander. He know his profession better than anyone I have met since.  The one thing he told me was that welding on forged parts takes a rigorous approach. He cut and shortened the pitman arm for this car. It took 2 hours. After preparing the thing and heating it in a500F oven he would then heat it until red-orange with his torch. He would then make a single pass on one side, then flip it over and make a single pass on the other.  Then stop, chip and wire brush both sides, heat it up and make another pass. All this took about an hour and a half. He then put it back into the oven and told to come back in later. He had me have it x-rayed and he looked over the results. Only then would he allow me to put it on the car. I have never to this day seen anyone else go through such a careful process when cutting and welding forged auto parts. I once asked Fatman about dropped spindles and their process. I did not like their answer.

 

For the last few decades I found a man here in San Francisco that was as good a welder as the ex-NASA ( Grumman ) welder.  He died a couple of years back and I have not found anyone to replace him. So, I have decided I need to get back to welding myself. I am ordering up a set of equipment both for Gas (hence reading Budd Davisson closely)  and MIG. I am hoping the many years of helping and observing both the NASA Welder and my friend will come in handy. Both of them told me that prep and procedure was the name of the game and the actual welding is just practice, practice, practice.

 

James.

 

 

[James_Douglas]

19 hours ago, Matt Wilson said:

I ended up selecting a similar Willwood master cylinder for my '49 Power Wagon.  I'm in the process of installing it now.  One thing I will point out is that my Willwood unit, and probably many other Willwood units, if not all of them, come with a disclaimer that says they are not DOT-approved for highway use, or similar wording.  I decided I wanted dual circuit brakes, and since an extensive search had not produced anything that would fit in that very tight space, I went ahead and purchased the Willwood unit. 

 

I've known of other people who have successfully used these units in vintage car applications for many years, and I think mine will work just fine and be every bit as reliable as any other master cylinder, but if I should get into a wreck, I could be under additional scrutiny by law enforcement, insurance and/or lawyers for having such a part on my truck.  I've heard of people's vintage or specialty cars being torn apart at the accident scene by investigators who were looking for modifications such as these, so don't he lulled into the mindset that they won't be discovered.  Eventually, I may try to find something else that is DOT-approved to fit the bill.  I just wanted everyone to be aware of this potential risk, and I'd also like to hear others' opinions and experiences in this regard.

That is why I have an umbrella policy....

[Matt Wilson]

1 hour ago, James_Douglas said:

That is why I have an umbrella policy....

Well, I plan to get full coverage on my Power Wagon, but I doubt that's the same as an umbrella policy.  I guess you mean an umbrella liability policy that is not just an auto policy, but rather a general coverage umbrella policy, that would kick in and provide coverage in the event someone were to successfully sue you over an auto-related accident (and would, of course provide coverage non-auto-related incidents)?  Sorry for my lack of understanding.

[40plyrod]

You mount looks similar to the one I made for my 40 plymouth. I had to heat the pedal arm to go past the master cylinder, maybe that and option for you too? Here's the link to my build the master cylinder upgrade is on the 1st page.

 

Edited February 16, 2020 by 40plyrod

[DJ194950]

Man oh man,

your work on those floors was absolutely top notch!!  ? ?

 

DJ

[40desoto]

2 hours ago, 40plyrod said:

You mount looks similar to the one I made for my 40 plymouth. I had to heat the pedal arm to go past the master cylinder, maybe that and option for you too? Here's the link to my build the master cylinder upgrade is on the 1st page.

 

Thanks for sharing 40plyrod. Wondering if you dont mind sharing how your brakes turned out, what calipers your using as well how you plumbed everything.

ie: residual valves, since the MC sits lower than the calipers, metering valve, combination valve/proportioning valve if needed?

 

 

[40plyrod]

The brakes work very well. I used mid 70's camero callipers and a 2lbs residual pressure valve on the front and nothing else.